There are several steps to setting up document approval for a specific list or library in SharePoint:

1. Create an approval workflow. You can create a custom workflow by using the SharePoint workflow platform. You can also add a workflow from the SharePoint Store or by using third-party workflow solutions.
2. Configure your workflow. You will need to set up the workflow based on your specific needs. This includes defining which users are approvers, who the workflow should notify, and how often the workflow should run.
3. Associating your workflow with the list or library. Finally, you need to associate the workflow with the list or library.